A. Field of the Invention
The present invention relates to processes for acid hydrolysis of biomass.
Attention is called to U.S. Pat. No. 4,237,226 (Grethlein), as well as the further art made of record therein, including the Thompson thesis which describes, among other things, a continuous plug-flow reactor that may be employed to practice the present invention. Attention is also called to a writing entitled "Pentosan Hydrolysis in a Concentrated Slurry System" (Horwarth et al)
B. Setting for the Invention
While the present invention has use in conjunction with other sugars than glucose, the production of glucose from the carbohydrates (e.g. cellulose) in biomass is discussed mostly hereinafter. (The term biomass includes plant materials, that is, any material that comes from photosynthesis and products derived therefrom, even in the waste state. Included in biomass are cellulose, including hemicellulose, other carbohydrates and proteins, lignins, and extractable (e.g., resins and tars.)) Among other things, conversion of cellulosic material to glucose, and subsequent fermentation to ethanol, is a method to utilize a portion of solid waste or biomass. Currently, the usual method used for cellulosic conversion involves acid hydrolysis of the cellulosic polymer, in water, at high temperature with dilute mineral acid; the cellulosic content is usually low due to difficulties of mixing and pumping a slurry containing more than 15% by weight dry biomass. About fifty percent of the potential glucose is actually converted in seconds, but by-product formation and high energy requirements presently limit use of this conversion mechanism.
C. Objects of the Invention
It is an objective of the present invention to provide a process for the acid hydrolysis of biomass for producing glucose and/or other sugars from carbohydrate components (e.g., cellulose) and the like therein.
Another objective is to provide a process for producing glucose and/or other sugars in which a non-aqueous support fluid is used as a means for producing a pumpable cellulosic substrate.
Still another objective is to provide a process for producing glucose and/or other sugars in which a non-aqueous support fluid is used as a way to reduce the amount of water involved in the acid hydrolysis of the biomass, thereby obtaining high sugar concentrations in the aqueous phase of the slurry.
A further objective is to provide other decomposition products of biomass (e.g., furfural).
These and still further objectives are addressed hereinafter.
D. Summary of the Invention
The foregoing objects are achieved in a continuous-flow conversion process by which biomass is converted by acid hydrolysis to glucose and/or other sugars, that comprises the steps of producing a slurry comprising biomass and a non-aqueous, liquid hydrocarbon or hydrocarbon derivative and an aqueous acid; rapidly heating the slurry to a temperature sufficient that hydrolysis of the carbohydrate component and the like of the biomass is realized but for a time interval sufficiently short to minimize decomposition of the sugars; quenching the reaction; and washing the post-reaction solids to remove the sugars therefrom.